Many people asked me to publish a walk through SHOW INNODB STATUS output, showing what you can learn from SHOW INNODB STATUS output and how to use this info to improve MySQL Performance.

To start with basics SHOW INNODB STATUS is command which prints out a lot of internal Innodb performance counters, statistics, information about transaction processing and all kinds of other things. In MySQL 5 number of Innodb performance counters were exported and now available in SHOW STATUS output. Most of them are same as you previously could find in SHOW INNODB STATUS, there are however few which were not available before.

In SHOW INNODB STATUS many values are per second. If you're planning to use these values make sure they are sampled over decent period of time. In the very start of printout Innodb will print:

PLAIN TEXT CODE:

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I finally took the time to upgrade my MySQL cluster to 5.11 beta in order to test some new features. I have some clusters running with 2 ndb_mgmd nodes , but the ones that are scheduled for upgrade only have 1 management node yet.

So todays goal was getting multinode namagement up and running on 5.11 , and test the fresh --nowait feature for ndbd. Digging back to my older docs told me this would be a 15 minute effort, I'd had to change the config file to have 2 management nodes, restart them. Then change the connection strings for the ndbd's so that they have 2 nodes. Solved.

The first thing I ran into was that on the 2nd node I couldn't connect to ndb_mgmd via ndb_mgm , I could connect to it from a remote machine or while specifying a full connection string with the external ip but not from internally. Off course this was a fine dns problem as it seemed the machine couldn't do lookups for localhost :)

The second thing I …

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Cacti is a complete network graphing solution designed to harness the power of RRDTool’s data storage and graphing functionality. Cacti provides a fast poller, advanced graph templating, multiple data acquisition methods, and user management features out of the box. All of this is wrapped in an intuitive, easy to use interface that makes sense for LAN-sized installations up to complex networks with hundreds of devices.

Cacti is a complete frontend to RRDTool, it stores all of the necessary information to create graphs and populate them with data in a MySQL database. The frontend is completely PHP driven. Along with being able to maintain Graphs, Data Sources, and Round Robin Archives in a database, cacti handles the data gathering. There is also SNMP support for those used to creating …

WebSite: www.mysql.com

The world’s most popular open source database.

I remember when MySQL was spreading rapidly, mostly due to its ease of use. That was long time ago, apparently. Now we are entering the dark ages of obscure settings, or so it seems, reading some MySQL Cluster setting definitions.
Quoting from the the manual:

TimeBetweenLocalCheckpoints

This parameter is an exception in that it does not specify a time to wait before starting a new local checkpoint; rather, it is used to ensure that local checkpoints are not performed in a cluster where relatively few updates are taking place. In most clusters with high update rates, it is likely that a new local checkpoint is started immediately after the previous one has been completed.

The size of all write operations executed since the start of the previous local checkpoints is added. This …

Have you seen recent eWeek benchmarks which test OpenSource stacks and compare them to .NET ? Here is what was compared and here are results.

Results make me ask number of questions - why WAMP would perform 6 times better than LAMP ? Why Python would be faster than PHP on Windows but slower on Linux ? Without having such basic questions answered I can't accept results as valid. If you run benchmark and something unexpected pops up drill it down - quite frequently it would be configuration problem, bug or something similar.

Well, this is however not my main concern with this benchmark. Here is to start:

No Specifications - Good benchmark starts with specifications. What …

MySQL on GNU/Linux appears to be able to either run multiple processes, or one process and multiple threads. We've noticed a significant CPU penalty for multiple processes, probably from the context switching overhead. The trouble was, one of our servers wouldn't use threads; it wanted to use multiple processes. This article explains how we got it to use threads instead.

One needs to be very careful before deleting files as once deleted the files are gone for good. A friend of mine today called as MySQL was failing to start on his server. Earlier when "cleaning" his server, he had deleted binary log files without fully understanding their role. When I logged in to his server, I noticed the following errors:

060716 17:21:53  mysqld started
060716 17:21:53  InnoDB: Started; log sequence number 0 1736000119
/usr/sbin/mysqld: File './mysql-bin.000002' not found (Errcode: 2)
060716 17:21:53 [ERROR] Failed to open log (file './mysql-bin.000002', errno 2)
060716 17:21:53 [ERROR] Could not open log file
060716 17:21:53 [ERROR] Can't init tc log
060716 17:21:53 [ERROR] Aborting

060716 17:21:53  InnoDB: Starting shutdown...
060716 17:21:55  InnoDB: Shutdown completed; log sequence number 0 1736000119
060716 17:21:55 [Note] /usr/sbin/mysqld: Shutdown complete
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